The invention relates to a polyurethane-acrylic composition and a method for making such a composition. More particularly, the invention relates to a flexible and elastic actinic radiation cured polyurethane acrylic copolymer containing a light scattering or fluorescing material.
Polyurethane-acrylic protective and decorative coating compositions are well known. Conventionally, ovens and infrared sources have been used to cure such compositions. Most recently, ultraviolet (U.V.) energy curing has been suggested, using various U.V. sensitizers for sensitizing photopolymerization in ultraviolet wavelengths in the near-visible region. The literature on such photopolymerization and sensitization is abundant.
Advantages of U.V. curing over other conventional curing in ovens or the like include significantly faster curing times, savings in energy requirements, elimination of air pollution, and ready availability of equipment.
One problem with prior art U.V. cured polyurethane acrylic compositions is that they are all hard and rigid or semi-rigid, thus making them less suitable for certain applications. For example, the rigidity of the prior art polyurethane-acrylic compositions precluded the production of relatively thick functional polyurethane-acrylic structures. Another more significant problem with these compositions exists in the photocuring process itself. Due to light obscuration by opaque components, there is generally difficulty in obtaining full and uniform cure of the composition.
Accordingly, it is an object of the present invention to provide a substantially improved actinic radiation process for the curing of polymers wherein the polymers are fully cured.
Another object of the invention is to provide polyurethane acrylic copolymers that are flexible, elastomeric and solvent-resistant.
A further object of the invention is to provide such polyurethane acrylic copolymers in an efficient, reliable and inexpensive manner.